The neutron capture cross sections of ${}^{74}\mathrm{Ge}$, ${}^{76}\mathrm{Ge}$, and ${}^{75}\mathrm{As}$ have been measured at the Karlsruhe Van de Graaff accelerator by means of the activation technique. The neutron source reaction ${}^7\mathrm{Li}(p,n){}^7\mathrm{Be}$ was used for simulating a thermal energy distribution for $\mathit{kT}=25$ keV to determine the astrophysically relevant stellar cross sections directly. Based on an extended series of activations, consistent results could be obtained, corresponding to Maxwellian average cross sections at $\mathit{kT}=30$ keV of $37.6\pm 3.9$ mb for ${}^{74}\mathrm{Ge}$, $21.5\pm 1.8$ mb for ${}^{76}\mathrm{Ge}$, and $362\pm 19$ mb for ${}^{75}\mathrm{As}$. These results are more accurate than previous data and are, therefore, important for resolving previous discrepancies. By extrapolation Maxwellian averaged cross sections were derived for thermal energies from 5 to 100 keV. The implications of these results for the $s$-process abundances in massive stars and for the background conditions in double $\beta$ decay experiments are discussed.

• Received 7 January 2009

DOI:https://doi.org/10.1103/PhysRevC.79.065802